Rechargeable battery

ABSTRACT

According to an embodiment of the present invention, a rechargeable battery includes a case, a first electrode coupled to the case, a second electrode coupled to the case and the second electrode having a portion extending outside of the case, a short bar electrically coupled to the portion of the second electrode, and an extensible member extending from the case and at least a portion of the short bar being on the extensible member with a gap therebetween. The extensible member is configured to couple the short bar electrically to the first electrode in response to an overcharging condition of the rechargeable battery, thereby short-circuiting the first and second electrodes via the short bar.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/701,401, filed Feb. 5, 2010, which claims priority to and the benefitof U.S. Provisional Patent Application No. 61/178,357, filed on May 14,2009, the entire content of both of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

An embodiment of the present invention relates to a rechargeablebattery, more particularly.

2. Description of the Related Art

Prismatic rechargeable batteries for hybrid electric vehicle (HEV) havea heat dissipation efficiency superior to cylindrical rechargeablebatteries, and have improved safety over the cylindrical rechargeablebatteries when overcharged.

Therefore, current interrupt devices (CIDs), which interrupt currentswhen the batteries are overcharged, are not applied to the prismaticrechargeable batteries for HEV.

However, plug in hybrid electric vehicles (PHEVs) and electric vehiclesas well as HEV demand high-capacity rechargeable batteries, such thatthe sizes of the batteries increase.

As such, the prismatic rechargeable batteries become thicker, and theirheat dissipation efficiencies are different depending on whether thebatteries are at the inside portion or at the outside portion of thebattery system. Therefore, it is difficult to secure the safety of thesebatteries of the power system when they are being overcharged.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the present invention,and therefore it may contain information that does not form the priorart that is already known in this country to a person of ordinary skillin the art.

SUMMARY OF THE INVENTION

An exemplary embodiment of the present invention is directed toward arechargeable battery which improve the safety of the rechargeablebattery when it is being overcharged by short-circuiting its outsideelectrode terminals and maintaining the short circuit state.

According to an embodiment of the present invention, a rechargeablebattery includes a case, a first electrode coupled to the case, a secondelectrode coupled to the case and the second electrode having a portionextending outside of the case, a short bar electrically coupled to saidportion of the second electrode, and an extensible member extending fromthe case and at least a portion of the short bar being on the extensiblemember with a gap therebetween. The extensible member is configured tocouple the short bar electrically to the first electrode in response toan overcharging condition of the rechargeable battery, therebyshort-circuiting the first and second electrodes via the short bar.

In one embodiment, the extensible member may include a extensible.

In one embodiment, the extensible member may be configured to extendtoward the short bar when an internal pressure of the case is above aset value.

In one embodiment, the extensible member may include an electricalconductor.

In one embodiment, the extensible member and the short bar may beconfigured to remain electrically coupled to each other in response tothe overcharging condition.

In one embodiment, at least one of the extensible member or the shortbar may be configured to melt when the extensible member and the shortbar conduct an electrical current in response to the overchargingcondition.

In one embodiment, the short bar may be welded and/or screwed to saidportion of the second electrode.

In one embodiment, the rechargeable battery may further include a springhaving two end portions with one of the end portions coupled to the caseand the other one of the end portions coupled to a side of theextensible member facing the short bar. The spring may be configured toapply a pressure on the extensible member in a direction toward the caseand away from the short bar.

In one embodiment, the spring may include two springs positioneddiametrically on the side of the extensible member facing the short bar.

In one embodiment, the pressure applied on the extensible member by thespring may be less than an internal pressure of the case applied on theextensible member when the rechargeable battery is in the overchargingcondition.

According to another embodiment of the present invention, a rechargeablebattery includes a case, a first electrode coupled to the case, a secondelectrode coupled to the case and the second electrode having a portionextending outside of the case, a third electrode coupled to the case andthe third electrode having a portion extending outside of the case, afirst short bar electrically coupled to said portion of the secondelectrode, a second short bar electrically coupled to said portion ofthe third electrode, the first short bar being adjacent to the secondshort bar with a gap therebetween, and an extensible member extendingfrom the case, the extensible member located below the first and secondshort bars with a gap therebetween. The extensible member is configuredto couple the first short bar electrically to the second short bar inresponse to an overcharging condition of the rechargeable battery,thereby short-circuiting the first and second electrodes via the firstand second short bars.

In one embodiment, the extensible member may include a extensible.

In one embodiment, the extensible member may be configured to extendtoward the first and second short bars when an internal pressure of thecase is above a set value.

In one embodiment, the second short bar may be between the first shortbar and the extensible member.

In one embodiment, the first and second short bars may be atsubstantially a same distance from the extensible member.

In one embodiment, the extensible member may include an electricalconductor.

In one embodiment, the rechargeable battery may further include aconduction plate on the extensible member, wherein the conduction plateis configured to electrically couple the first and second short barstogether in response to the overcharging condition.

In one embodiment, the first and second short bars may be configured toremain electrically coupled to each other in response to theovercharging condition.

In one embodiment, at least one of the first short bar or the secondshort bar may be configured to melt when the first short bar and thesecond short bar conduct an electrical current in response to theovercharging condition.

In one embodiment, the first short bar may be welded and/or screwed tosaid portion of the second electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a rechargeable batteryaccording to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the rechargeable batterytaken along the line II-II of FIG. 1.

FIG. 3 is a schematic cross-sectional view showing a short circuit stateof the electrode terminals when the internal pressure of therechargeable battery increases.

FIG. 4 is a schematic cross-sectional view showing a rechargeablebattery according to another embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view showing a rechargeablebattery according to another embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view showing a rechargeablebattery according to another embodiment of the present invention.

FIG. 7 is a graph showing decrease of voltage and temperature due to ashort circuit at the outside terminals of a rechargeable batteryaccording to an embodiment of the present invention.

<Description of Reference Numerals Indicating Elements in the Drawings>100, 200, 300, 400: rechargeable battery 10: electrode assembly 11:positive electrode 12: negative electrode 111, 121: uncoated region 13:separator 20: case 30: cap plate 31, 36: terminal hole 32: electrolyteinjection hole 33: sealing plug 34: vent portion 35: through hole 41,42: first electrode, second electrode 43: interposing insulator 51, 52:lead member 50, 53, 54: extensible member 55: conduction plate 61: shortbar 71: plate spring 72: support member 81, 91: first short bar 82, 92:second short bar 83, 93: assistance electrode C: gap C1, C2, C3: firstgap, second gap, third gap

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. As those skilled in the art would realize,the described embodiments may be modified in various different ways, allwithout departing from the spirit or scope of the present invention. Thedrawings and description are to be regarded as illustrative in natureand not restrictive. Like reference numerals designate like elementsthroughout the specification.

FIG. 1 is a schematic perspective view of a rechargeable battery 100according to an embodiment of the present invention, and FIG. 2 is aschematic cross-sectional view of the rechargeable battery 100 takenalong the line II-II of FIG. 1.

Referring to FIGS. 1 and 2, the rechargeable battery 100 includes a case20 in which an electrode assembly 10 is enclosed, a cap plate 30 whichcloses up an opening formed at a side of the case 20, a first electrodeterminal 41 and a second electrode terminal 42 fitted in terminal holes31 and 36, respectively, of the cap plate 30, and lead members 51 and 52connecting the first and second electrode terminals 41 and 42,respectively, to the electrode assembly 10.

The electrode assembly 10 includes a separator 13 as an insulator, and apositive electrode 11 and a negative electrode 12 respectively locatedat opposite sides of the separator 13. The positive electrode 11, thenegative electrode 12 and the separator 13 are rolled up together toform a jelly roll shape.

The positive electrode 11 and the negative electrode 12 are formed withcurrent collectors of thin plated metallic foils. Each of the positiveand negative electrodes 11 and 12 is partitioned to have a coated regionand uncoated regions 111 and 121 which are partitioned by whether tocoat active material. That is, the coated region is an area coated withthe active material, and the uncoated regions 111 and 121 are areas thatare not coated with the active material.

Each pair of the uncoated regions 111 and 121 are at opposite ends toeach other and located at the longitudinal (or horizontal) opposite endsof the positive electrode 11 and the negative electrode 12. The uncoatedregions 111 and 121 are connected to the lead members 51 and 52,respectively, and the lead members 51 and 52 are then connected to thefirst and second electrode terminals 41 and 42, respectively.

The case 20 forms an external appearance or shape of the rechargeablebattery 100, and is formed by, for example, an electrically conductivemetal such as aluminum, aluminum alloy or nickel-plated steel. The case20 provides a space in which the electrode assembly 10 is enclosed, andmay be formed as a prismatic case, for instance, in a shape ofhexahedron. The prismatic case 20 has a wider heat dissipating area andis superior to a cylindrical case in heat dissipation efficiency.

The cap plate 30 is formed by a thin plate, and is fitted into theopening formed at a side of the case 20, thereby closing up the opening.The cap plate 30 has an electrolyte injection hole 32 for injecting theelectrolyte into the inside of the case 20 closed by the cap plate 30.The electrolyte injection hole 32 is sealed up with a sealing plug 33after injecting the electrolyte.

Further, in order to prevent or reduce the likelihood of explosion ofthe rechargeable battery 100 due to an increase of its internalpressure, the cap plate 30 has a vent portion 34 that would be torn outor ruptured when the internal pressure reaches a set or predeterminedvalue, thereby allowing internal gas to be discharged.

In addition, in order to improve safety when the rechargeable battery100 is overcharged, the rechargeable battery 100 is configured toshort-circuit the first and the second electrode terminals 41 and 42 atthe outside of the case 20. Further, the rechargeable battery 100 isconfigured to firmly maintain the short circuit state of the first andthe second electrode terminals 41 and 42, thereby preventing the shortcircuit state from returning to a release state (or open circuit state).

For instance, the positive electrode 11 of the electrode assembly 10 isconnected to the first electrode terminal 41 via the lead member 51, andthe negative electrode 12 is connected to the second electrode terminal42 via the lead member 52.

The first electrode terminal 41 is inserted into the terminal hole 31 ofthe cap plate 30, thereby being electrically or conductively connectedto the cap plate 30. The first electrode terminal 41 may be welded tothe cap plate 30 while being inserted into the terminal hole 31. Thus,the cap plate 30 and the first electrode terminal 41 are charged with apositive voltage. In addition, the case 20 may be electrically orconductively connected to the cap plate 30.

The second electrode terminal 42 is inserted into the terminal hole 36with an interposing insulator 43, such that the second electrodeterminal 42 is kept electrically insulated from the cap plate 30. Hence,the second electrode terminal 42 is charged with a negative voltage, andis kept electrically insulated from the first electrode terminal 41 andthe cap plate 30.

The rechargeable battery 100 includes a suitable extensible member 50,e.g., a bellows member or bellows, which is configured to short-circuita portion that is electrically or conductively connected to the firstelectrode terminal 41 and a portion that is electrically or conductivelyconnected to the second electrode terminal 42 when the internal pressurereaches a set value.

The rechargeable battery 100 further includes a short bar 61 which formsa short circuit configuration with the extensible member 50 when therechargeable battery 100 is overcharged. That is, the extensible member50 is connected to the first electrode terminal 41 via the cap plate 30,and the short bar 61 is directly and electrically connected to thesecond electrode terminal 42.

The cap plate 30 has a through hole 35 at a portion adjacent to thesecond electrode terminal 42. The extensible member 50 is fixated on thecap plate 30 to cover the through hole 35. Accordingly, the internalpressure of the rechargeable battery 100 may work at the extensiblemember 50 through the through hole 35.

While the rechargeable battery 100 is operated normally, and thus theinternal pressure remains within a normal range, the extensible member50 remains at a contracted state (see FIG. 2). The extensible member 50may be extended to contact the short bar 61 resulting inshort-circuiting when the internal pressure goes over a set orpredetermined value.

The extensible member 50 may be made from an electrically conductivematerial such as aluminum or metallic material. Further, the extensiblemember 50 may be welded to the cap plate 30 to thereby form anelectrically conductive structure with the cap plate 30. Consideringweldability, the extensible member 50 may be made from the same materialas the cap plate 30.

Since the extensible member 50 is electrically or conductively connectedto the cap plate 30, the extensible member 50 is substantially andelectrically connected to the positive electrode 11 of the electrodeassembly 10 via the lead member 51 of the first electrode terminal 41and the uncoated region 111.

In the embodiment illustrated in FIG. 2, the cap plate 30 and the firstelectrode terminal 41 are connected to the positive electrode 11, andthe second electrode terminal 42 is electrically insulated from the capplate 30 and connected to the negative electrode 12. However, aconfiguration in which the above described connections of the first andsecond electrode terminals are reversed is also possible and is withinthe scope of the present invention.

As illustrated in the embodiment shown in FIG. 2, the rechargeablebattery 100 in which the cap plate 30 and the case 20 are electricallyconnected to the positive electrode 11 may have a better heatdissipation efficiency when compared to a rechargeable battery in whichthe cap plate 30 and the case 20 are electrically connected to thenegative electrode 12. Referring to the graph of FIG. 7, temperature (a)changes after short-circuiting the rechargeable battery 100 at the sideof the negative electrode 12 are less significant than that of thetemperature (c) changes after short-circuiting the rechargeable battery100 at the side of the positive electrode 11.

One end of the short bar 61 is fixed at the second electrode terminal42, and the other end of the short bar 61 is extended in a directionacross the end of the extensible member 50. An end portion of the shortbar 61 is on or faces the extensible member 50. Accordingly, the shortbar 61 may contact the extensible member 50 or be separated from theextensible member 50 depending upon the expansion or contraction of theextensible member 50.

For example, the short bar 61 is coupled with screws to the secondelectrode terminal 42 and electrically connected to the second electrodeterminal 42. Further, the short bar 61 may be welded to the secondelectrode terminal 42, or both screw coupling and welding may beperformed.

Accordingly, the positive electrode 11 of the electrode assembly 10 iselectrically connected to the extensible member 50 via the lead member51, the first electrode terminal 41 and the cap plate 30, and thenegative electrode 12 is electrically connected to the short bar 61 viathe lead member 52 and the second electrode terminal 42.

While the internal pressure of the rechargeable battery 100 remainswithin the normal range, the extensible member 50 is separated from theshort bar 61 with a gap C therebetween.

FIG. 3 is a schematic cross-sectional view showing a short circuit stateof the electrode terminals when the internal pressure of therechargeable battery increases. Referring to FIG. 3, the internalpressure of the rechargeable battery 100 exceeds the normal range, suchthat the extensible member 50 is extended to thereby be short-circuitedwith the short bar 61. Accordingly, the rechargeable battery 100 may bereleased from an overcharging state.

The extensible member 50 and the short bar 61 are short-circuited andmelted to be stuck to each other, such that the rechargeable battery 100maintains the short circuit state. That is, the rechargeable battery 100does not return to the overcharged state. For example, the temperaturesof the extensible member 50 and the short bar 61 are suitably increaseddue to their resistances to a short circuit current to melt and couplethe extensible member 50 to the short bar 61.

FIG. 7 is a graph showing decreases of voltage and temperature due to ashort circuit at the outside terminals of a rechargeable battery.Referring to FIG. 7, a result of a short circuit experiment isexhibited. In the experiment, a lead storage battery was overcharged at36A, and a positive electrode and a negative electrode wereshort-circuited with each other using an electrically conductive memberof 0.05 mΩ before the vent was operated.

Referring to the graph of FIG. 7, the voltage (b) of the lead storagebattery rapidly dropped to 0 V, and the temperature (c) at the side ofthe positive electrode increased rapidly and then decreased rapidly,when the short circuit occurred. The temperature (a) at the side of thenegative electrode remains substantially steady.

In view of the foregoing, it was confirmed from the above describedexperiment that the exterior short-circuit configuration like theembodiment shown in FIG. 1 could improve the safety of the rechargeablebattery 100 when overcharged.

Hereinafter, various other embodiments of the present invention will bedescribed. Descriptions about the same or similar elements as theembodiment shown in FIG. 1 would not be described again in detail, andelements different from each other will be described in more detail.

FIG. 4 is a schematic cross-sectional view showing a rechargeablebattery 200 according to another embodiment of the present invention.Referring to FIG. 4, the rechargeable battery 200 in accordance with theembodiment shown in FIG. 4 further includes a plate spring 71 which isfixated on the cap plate 30 and supports the extensible member 50 at itsfree end.

In more detail, the plate spring 71 is provided to the upper side of theextensible member 50 that is cylindrically shaped, and may support theextensible member 50 in a downward direction toward the cap plate 30. Inthe embodiment shown in FIG. 4, a pair of plate springs 71 is providedat diametrically opposing sides of the upper side of the extensiblemember 50, such that the upper side of the extensible member 50 isbalanced by the pair of plate springs 71.

Accordingly, the plate spring 71 may be fixated to the cap plate 30 withan interposing support member 72. That is, the support member 72 isfixed on the cap plate 30, and then one end of the plate spring 71 isfixed on the support member 72. Further, the plate spring 71 supportsthe upper side of the extensible member 50 by the other end. Here, thecombined height of the support member 72 and the plate spring 71 issubstantially the same as the height of the extensible member 50 whencontracted.

The rechargeable battery 200 of the embodiment shown in FIG. 4 mayprevent the extensible member 50 from being extended to beshort-circuited with the short bar 61 due to a shock or a vibration,when the internal pressure of the rechargeable battery 200 remainswithin a normal range.

The plate spring 71 applies a suitable amount of its elastic or springforce to maintain the extensible member 50 in the contracted state whilethe internal pressure of the rechargeable battery 200 is within thenormal range, and to allow the extensible member 50 to extend and pushaway the plate spring 71 when the internal pressure exceeds the normalrange. Hence, the plate spring 71 does not disturb the extension of theextensible member 50 when the internal pressure of the rechargeablebattery 200 increases, and still also prevent or protect the extensiblemember 50 from mis-contacting with the short bar 61 when the internalpressure is within the normal range.

FIG. 5 is a schematic cross-sectional view showing a rechargeablebattery 300 according to another embodiment of the present invention.Referring to FIG. 5, the rechargeable battery 300 in accordance with theembodiment shown in FIG. 5 includes a extensible member 53, a firstshort bar 81 and a second short bar 82 such that a portion which iselectrically or conductively connected to the first electrode terminal41 and a portion which is electrically or conductively connected to thesecond electrode terminal 42 are short-circuited with each other whenthe internal pressure increases.

In the rechargeable battery 100 of the embodiment shown in FIGS. 1-3,the extensible member 50 is made from an electrically conductivematerial to thereby be short-circuited directly with the short bar 61.Instead, in the rechargeable battery 300 of the embodiment shown in FIG.5, the first short bar 81 is electrically or conductively connected tothe first electrode terminal 41 and the cap plate 30, and the secondshort bar 82 is electrically or conductively connected to the secondelectrode terminal 42, such that the first short bar 81 and the secondshort bar 82 are configured to be short-circuited directly with eachother by utilizing the extensible member 53.

For this operation, the first short bar 81 is fixated on an assistanceelectrode 83, and a portion of the first short bar 81 is on or faces theextensible member 53 with a first gap C1 therebetween on an extensionline of the extensible member 53 in a direction of extension. Forexample, the assistance electrode 83 is electrically or conductivelyconnected to the cap plate 30, and the first short bar 81 isscrew-coupled to the assistance electrode 83. The first short bar 81 maybe welded to the assistance electrode 83 or may be screw-coupled andwelded at the same time.

The second short bar 82 is fixated on the second electrode terminal 42,and a portion of the second short bar 82 is on or faces a portion of thefirst short bar 81 with a second gap C2 therebetween on the extensionline of the extensible member 53 in the direction of extension. That is,the extensible member 53, the first short bar 81 and the second shortbar 82 are arranged on the extension line of the extensible member 53with the first gap C1 and the second gap C2 therebetween.

Accordingly, while the internal pressure of the rechargeable battery 300remains within the normal range, the extensible member 53, the firstshort bar 81 and the second short bar 82 are kept insulated from oneanother by maintaining the first gap C1 and the second gap C2. However,when the internal pressure exceeds the normal range, the extensiblemember 53 is extended to closely contact with the first short bar 81,and is extended further to thereby raise the first short bar 81 toshort-circuit the first short bar 81 with the second short bar 82.

In the rechargeable batteries 100 and 200 of the embodiments shown inFIGS. 1-4, the extensible member 50 is made from a suitable electricallyconductive material since the extensible member 50 is electricallyconducted to thereby form a short circuit configuration. However, in therechargeable battery 300 of the embodiment shown in FIG. 5, theextensible member 53 may be made from an electrically insulationmaterial because the extensible member 53 does not need to beelectrically conducted with the first short bar 81 or the second shortbar 82.

FIG. 6 is a schematic cross-sectional view of a rechargeable battery 400according to another embodiment of the present invention. Referring toFIG. 6, the rechargeable battery 400 of this embodiment includes aextensible member 54, a conduction plate 55, a first short bar 91 and asecond short bar 92 such that a portion which is electrically orconductively connected to the first electrode terminal 41 and a portionwhich is electrically or conductively connected to the second electrodeterminal 42 are short-circuited with each other when an internalpressure of the rechargeable battery 400 reaches a set value.

The rechargeable battery 300 of the embodiment shown in FIG. 5 has aconfiguration including the first short bar 81 and the second short bar82 which are short-circuited as the extensible member 53 is extended.Instead, the rechargeable battery 400 of the embodiment shown in FIG. 6has a configuration that the first short bar 91 and the short bar 92 areshort-circuited through an electrical conduction structure such as theconduction plate 55 which is located on an upper side of the extensiblemember 54 as the extensible member 54 is extended.

For this operation, the first short bar 91 and the second short bar 92are located at substantially the same height from the conduction plate55 of the extensible member 54. The first short bar 91 is fixated on anassistance electrode 93, and a portion of the first short bar 91 is onor faces the upper side of the extensible member 54 with a third gap C3therebetween on an extension line of the extensible member 54 in adirection of extension.

The second short bar 92 is fixated on the second electrode terminal 42,and a portion of the second short bar 92 is on or faces the upper sideof the extensible member 54 with the third gap C3 therebetween on theextension line of the extensible member 54 in the direction ofextension. That is, the gap between the first short bar 91 and theextensible member 54 and the gap between the second short bar 92 and theextensible member 54 are substantially the same as the third gap C3. Thefirst short bar 91 and the second short bar 92 are on or face differentportions of the upper side of the extensible member 54.

Accordingly, while the internal pressure of the rechargeable battery 400remains within a normal range, the extensible member 54 is keptelectrically insulated from the first short bar 91 and the second shortbar 92 while being spaced apart by the third gap C3. However, when theinternal pressure of the rechargeable battery 400 exceeds the normalrange, the extensible member 54 is extended to thereby short-circuit theconduction plate 55 provided on the upper side of the extensible member54 with the first short bar 91 and the second short bar 92.

In the rechargeable battery 300 of the embodiment shown in FIG. 5, theextensible member 53 raises the first short bar 81 to short-circuit withthe second short bar 82, such that the first short bar 81 and the secondshort bar 82 are directly short-circuited. Instead, in the rechargeablebattery 400 of the embodiment shown in FIG. 6, the extensible member 54raises the conduction plate 55 to thereby short-circuit the first shortbar 91 with the second short bar 92 via the conduction plate 55.

In the rechargeable batteries 300 and 400 of the embodiments shown inFIGS. 5 and 6, the extensible member 53 and 54 may be formed withvarious suitable materials other than an electrically conductivematerial.

While the present invention has been described in connection with whatis presently considered to be practical exemplary embodiments, it is tobe understood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims and their equivalents.

What is claimed is:
 1. A rechargeable battery comprising: a case; afirst electrode coupled to the case; a second electrode coupled to thecase, the second electrode having a portion extending outside of thecase; a short bar electrically coupled to said portion of the secondelectrode; and an extensible member extending from the case, at least aportion of the short bar being on the extensible member with a gaptherebetween, wherein the extensible member is configured to couple theshort bar electrically to the first electrode in response to anovercharging condition of the rechargeable battery, therebyshort-circuiting the first and second electrodes via the short bar.